This invention pertains to a method and apparatus for manufacturing plastic bottles from molded hollow preforms. It can be applied particularly to facilities for the manufacture of plastic bottles by the biaxial stretching of the material, beginning from preforms in the shape of a hollow cylinder closed at one end. The preforms may be made in multi-cavity molds into which plastic material is injected around a central core. Each such mold is composed of two halves that are separated when the injection is completed in order to release the preforms, which resemble test tubes in shape.
In the conventional process, after removal from the mold the preforms are immediately transferred to a cooling platform that forms part of the machine to which the mold belongs, and which statically cools the preforms inside and out using open ventilation. Such cooling is indispensable if the preforms are to keep their shape during later handling operations.
The current method of cooling the preforms considerably reduces the production tempo of the molds in which they are produced because of the relatively long period of time the preforms spend on the stationary cooling platform that lies downstream from the molds and upon which every preform leaving the molds must be cooled before being moved off to its final destination. This method of cooling creates a bottleneck downstream from the injection molds.
Once the cooling operation is completed, pneumatic suction grips remove the preforms from the cooling platform and deliver them to their final destination, while a new run of preforms is injected into the mold. During such handling two types of pneumatic grips may be used, with one gripping the preform from the outside and the other taking it from the inside, turning it over and arranging it vertically on a conveyor.